This invention relates to methods and apparatus for testing substrates of hybrid circuits, and more particularly, to a method and apparatus of testing for short circuits and for open circuits that employs electrically generated electron bombardment techniques.
Complex hybrids require that the substrates be fully tested for short and open circuits to obtain an acceptable yield. Currently it is difficult to test substrates having many networks and many bonding pads. The existing testers use two probes, one connected to each bonding pad, to test whether there is electrical connection between the pads. In order to perform a complete test to verify that there are no open connections within a network and no shorts between networks, it is necessary to probe every combination of two networks. This method of testing is very time consuming. For example, large hybrids have about 300 networks, and when testing with two probes for short circuits between each possible pair of networks, many thousands of tests must be made.
It would be highly desirable to have improved methods and apparatus for performing such tests. Accordingly, it is an objective of the present invention to provide a method for testing a plurality of interconnection networks on a hybrid substrate that can be accomplished easily and rapidly. Another objective of the invention is the provision of apparatus for detecting circuit flaws in a plurality of interconnection networks on a hybrid substrate without individually testing every possible combination of two networks. A further objective of the present invention is to provide apparatus for detecting short circuits between pairs of networks or open pads on a network by probing only once on each network.